The disposal of animal waste has become a very important issue in intensive animal farming. The excreta of various intensively farmed animals, though rich in nutrients, is potentially polluting to the environment. For example, nitrogen and phosphorous compounds from cow, horse and swine manure can contaminate surface water and can even leach into groundwater. Ammonia and methane gas given off from stored manure or slurry can cause respiratory distress to people and animals in the local vicinity. As a result, there is a drive to put animal waste to beneficial uses, to reduce the amount disposed of and/or stored and thereby reduce some of the negative impacts intensive farming can have on the environment. Finding viable uses for animal waste, particularly uses that might consume the vast quantities of manure produced on moderate and large farms, would reduce the need for other disposal methods and would eliminate such waste as a source of pollution. Animal waste is also a very readily renewable resource, so supplies are beneficially fairly consistent and predictable.
In present research conducted by entities such as Innoventor, Inc. (St. Louis, Mo.), animal waste (e.g., manure) has been converted to a resinous hydrocarbon substance through energy conversion processes subjecting the animal waste to high pressures or high temperatures or both, typically under anaerobic conditions. It is believed that, under the application of pressure and/or temperature, larger hydrocarbon chains present in the animal waste break down into smaller chain hydrocarbon molecules. Much of the liquid content is driven off, and the result is a resinous product that is hereinafter referred to as “bio-oil.” The general processes for the creation of this bio-oil is found disclosed in U.S. Pat. Nos. 7,105,088, 7,597,812, and 7,985,345. Processing parameters and equipment are disclosed in Ocfemia, K. S., Zhang, Y. H., and Funk, T. (2006), Hydrothermal processing of Swine Manure into Oil Using a Continuous Reactor System: Development and Testing, Transactions of ASAE 49(2), 533-541 and Ocfemia, K. S., Zhang, Y. H., and Funk, T. (2006), Hydrothermal Processing of Swine Manure to Oil Using a Continuous Reactor System-Effects of Operating Parameters on Oil Yield and Quality, Transactions of ASAE 49(6), 1897-1904, both of which are incorporated herein by reference in their entirety. Currently, acceptable bio-oil is produced by Advanced BioRefinery Inc. (Ottawa, Canada).
Certain entities are currently researching the use of this bio-oil in asphalt binders. An asphalt mixture typically includes an asphalt binder mixture comprised mainly of petroleum-based asphalt binder, and aggregate, the asphalt binder mixture serving to bind the aggregate together. The resinous, tarry look and feel of the bio-oil sourced from animal waste suggests that it might serve as a replacement or as a substitute for asphalt, and, indeed, Innoventor, Inc., in its U.S. Pat. No. 7,985,345 broadly mentions the use of bio-oil as a potential substitute for all or a portion of petroleum-based asphalt binder in an asphalt mixture. However, research by the present inventor shows that bio-oil does not durably blend with petroleum-based asphalt binders, calling into question the broad statements made in the referenced patent. Notably, the cited patent is silent on the incompatibility of bio-oil with asphalt, and does not provide any working examples. It appears that the inventors of that patent simply saw that the bio-oil looked like asphalt, and therefore broadly stated that bio-oil could serve as a substitute, without any real data supporting this contention. Indeed, the cited patent only discloses the partial or full replacement of asphalt binder by bio-oil in very broad and general terms, and fails to provide any working example. The cited patent very broadly discloses an asphalt mixture of petroleum-based asphalt binder, bio-oil and aggregate, but upon testing, the bio-oil separates from the asphalt binder, thus failing to serve as a ready substitute for all or a partial amount of the asphalt. This failure is shown herein, and the present invention provides for better compatibility between asphalt and the bio-oil.
The use of bio-oil as a partial substitute for asphalt components is still of great interest, because, if successfully implemented, it would put animal waste to beneficial use. Thus, there is a need in the art to solve the problem encountered in attempting to incorporate bio-oil in an asphalt component. Particularly, there is a need in the art to prevent the separation of bio-oil from asphalt components so that the bio-oil may be successfully employed and may find commercial use.